Non-monotonic confinement effects on methane hydrate nucleation in silica slit pores

Abstract

Methane hydrate nucleation in silica slit pores of 1-5 nm width is investigated by molecular dynamics simulations at temperatures between 250 and 295 K. Three-dimensional radial distribution functions reveal progressive suppression of hydrate-like structural order with decreasing pore width, with nucleation inhibited below a critical width between 2 and 3 nm. Projected two-dimensional radial distribution functions and spatially resolved F3 and F4 order parameter profiles show that, under strong confinement, pronounced in-plane organization persists while three-dimensional clathrate connectivity is absent. These structural descriptors provide a simple criterion for identifying the critical pore width below which hydrate nucleation is suppressed.